The Pentagon's most advanced fighter plane made its combat debut in the U.S.-led strikes on Syria overnight, serving a crucial purpose for a sensitive mission that depended on stealth.

Pilots flying the F-22 Raptor flew bombing runs over Syria to target the militant Islamic State group, U.S. officials said.

Officials didn't say what targets the F-22 struck, but said it was used later in the series of strikes, which lasted several hours.

The plane is one of the country's most expensive—the F-22 program has cost $67 billion and only 188 planes have been built—but U.S. policymakers have been reluctant to use it in combat, in part because its high-end capabilities weren't needed for militant threats that the U.S. has been focused on for the last decade.

"The ultimate decision being made—that we are to use this aircraft against an adversary—is a unique and momentous decision for the United States Air Force," said an Air Force official.

Military officials said the planes ability to avoid detection by the advanced Syrian air defense systems was one reason to use the plane. But the plane's ability to fly higher and faster than other fighters also allows it to drop its 1000-pound guided bomb from a much further distance than older fighter planes, Air Force officials said.

According to the unclassified specifications of the plane, an F-22 can drop a precision bomb from at least 15 miles away from its target.

"It has a unique ability to approach adversaries in a way legacy aircraft can't," said the Air Force official. "There are things the F-22 is uniquely suited to address that the other fighters in our inventory can't."